This invention relates to fabricated, sheet metal assemblies, and, more particularly, to a sheet metal drive disc-pulley assembly designed for rotation by a V-belt to drive a friction wheel in a drive assembly such as that used in a lawn mower or garden tractor.
Previously known power drive discs which included V-belt, pulley grooves for rotation of the discs were typically aluminum or zinc castings. Such castings were both expensive to manufacture and less than desirable in operation inasmuch as cast aluminum or zinc are soft, brittle and weak and require a separate, sheet steel or other covering on the friction wheel drive surface to enable proper operation without high wear over long periods.
Another specific problem with previously known aluminum cast drive discs was the difficulty in retaining proper lubricant within the multi-row bearing units used to support such castings. Often, a felt ring was used as a portion of a labyrinth seal adjacent the lower end of such multi-row bearing units. The felt ring tended to withdraw and absorb lubricant from the race areas of the bearing during use and especially the upper row of ball bearings in such units. Accordingly, it was found that the prior aluminum cast drive discs failed prematurely because of an inability to retain proper lubricant within the bearings of the structure.
A less expensive substitute for the aluminum or zinc castings were desired. However, no fabricated, sheet metal pulleys which also included friction wheel drive disc areas were available. Although numerous sheet metal pulleys had been previously devised, none were available which could provide a friction wheel engaging disc, especially one which could withstand the necessary loads imposed thereon especially at the periphery at the drive disc for high speed drive engagement. In addition, no sheet metal pulleys were available including drive discs and which also provided adequate support for ball-type or other bearings needed to support the rotatable drive disc.
In keeping with the low cost objective for the fabricated sheet metal drive disc-pulley assembly, it was desired to use other than high precision bearing units. Because such semi-precision bearings often include slight eccentricities in the dimensions of their bearing races, the drive disc-pulley assembly was also required to overcome such eccentricities which otherwise could cause rotational wobble during use of the rotatable assembly. In addition, proper, coaxial alignment of the bearings was required with respect to one another and to the support shaft or axle since misalignment of the bearings can also cause wobbling, vibration, excessive bearing wear and result in premature failure.
Therefore, a need was evident for a low cost, fabricated, sheet metal drive disc-pulley assembly which could adequately support the necessary bearings as well as the loads and stresses imposed by the friction wheels engaged with the assembly, avoid rotational wobble during use because of any bearing eccentricities or misalignment, and retain lubricant properly within the bearings throughout the life of the assembly. The present invention in its various forms was conceived and built in recognition of and as a solution for such needs.